Lubrication performance of pipejacking in soft alluvial deposits

Cheng, Wen-Chieh; Wang, Lin; Xue, Zhong-Fei; Ni, James C.; Rahman, M.F.; Arulrajah, Arul

doi:10.1016/j.tust.2019.102991

Cited by 70 publications

(20 citation statements)

References 34 publications

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“…e reasons for the large differences between model tests and numerical simulations are as follows: ① Model test similarity ratio: the numerical simulation is based on the original size, and the model test uses a geometric similarity ratio of 1/30 and a physical mechanical parameter similarity ratio of 1. ② Soil properties: according to previous studies [22][23][24], differences in soil properties may have large experimental deviations. ③ Boundary conditions: numerical simulations simplify field boundary conditions, while model tests are constrained according to plane strain conditions.…”

Section: Tunnelmentioning

confidence: 97%

Instability Mechanism of Cavity‐Bearing Formation under Tunnel Excavation Disturbance

Liu

Wang

et al. 2020

Advances in Civil Engineering

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Urban subway construction inevitably causes disturbances to the rock strata. It can even cause ground collapse accidents when construction encounters a bad geological body in the stratum. To verify the influence of cavities on surface settlement and the mechanism of formation instability, the instability mechanism of cavity-bearing strata under tunnel excavation disturbance was herein studied by tests using self-designed indoor models and numerical simulations. This study was based on the concrete project case of Qingdao Metro. Two groups of experiments (with and without cavities) were designed to simulate the four-step excavation by staged unloading of an airbag. The results show that the settlement value in the cavity state was about twice as much as that in the nonvoid state at the same stage. Besides the first step of excavation, in the numerical simulation, the settlement value of the same stage is about 1.3 times that of the model test. Simulating the deformation process of the surrounding rock in model tests shows that, in the excavation of the tunnel, the collapse surface of the tunnel arch roof will be connected with the sliding surface of the formation cavity. The cavity will gradually change from a regular circle to an ellipse or may even close, resulting in a sudden increase in land subsidence or even ground collapse. This indicates that disturbance during tunnel excavation would cause greater instability in a stratum when bad geological bodies, such as cavities, exist in the stratum.

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Section: Tunnelmentioning

confidence: 97%

Instability Mechanism of Cavity‐Bearing Formation under Tunnel Excavation Disturbance

Liu

Wang

et al. 2020

Advances in Civil Engineering

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“…Since rapid urbanisation has significantly impacted surrounding environments [1][2][3][4][5][6][7], environment-friendly construction material may ease the impacts despite many advanced technologies available for environmental protection [8][9][10][11][12]. The strength and microstructure properties of spent coffee grounds (CG) stabilised with rice husk ash (RHA) were investigated, which are organic wastes derived from agricultural products [13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Using Post-Harvest Waste to Improve Shearing Behaviour of Loess and Its Validation by Multiscale Direct Shear Tests

et al. 2019

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Loess and PHW (post-harvest waste) are easily accessible in the Chinese Loess Plateau and have been widely applied to construction of residential houses that have been inhabited for decades under the effect of freeze-thaw cycles. Although many researchers have recognised that the addition of fibers to loess soil is effective in preventing soil erosion and stabilising slopes, a consensus on this claim has not been reached yet. This study investigates the shearing behaviour of the loess-PHW mixture using small-scale and large-scale direct shear (SSDS and LSDS) tests. Four typical shear stress versus horizontal displacement curves from the multiscale direct shear tests are recognised where one is featured with strain-softening shape and the other three with a strain-hardening shape. Two out of the three curves with strain-hardening shape show a gradual increase in the shear stress at additional and larger displacements, respectively, in which some factor starts to have an influence on the shearing behaviour. Comparisons of the shear strength measured in SSDS and LSDS are made, indicating that there are differences between SSDS and LSDS. The effect of PHW addition on shear strength is assessed in order to determine the optimal dosage. The improvement of shear strength is attributed to the effect of particle inter-locking, resulting from the addition of PHW to loess specimens, and takes effect as the water content surpassed a threshold, i.e., >14%, that facilitates particle rearrangement. Particle-box interaction behaviour is assessed at the same time, and the findings satisfactorily address the main cause of the gradual increase in shear stress following the curve inflection point. The improved shearing behaviour proves the ability of the loess-PHW mixture to resist the seepage force and consequently stratum erosion.

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“…Tan and Lu [5] indicated that a flawed slab connector embedded in the silt and sand layers has been deemed as being the main cause to lead to a sudden outburst of groundwater while deepening a subway excavation in Shanghai, China. e above studies indicate that incident often occurs, accompanied with significant casualties and economic losses, while developing infrastructure in urban areas [6][7][8][9][10][11][12][13][14][15] and relates mostly the phenomenon of water leak despite several protective measures available [15][16][17][18][19][20][21][22][23]. In spite that serious attention has been drawn, consensus on prevention and mitigation measures has not reached yet.…”

Section: Introductionmentioning

confidence: 99%

Rethinking the Water Leak Incident of Tunnel LUO09 to Prepare for a Challenging Future

Cheng

Zhou³

et al. 2019

Advances in Civil Engineering

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Incident often occurs while deepening excavation pit and/or tunnelling underground pipelines although serious attention from practitioners, engineers, and scientists has received. Prevention and mitigation of incident have thus been deemed to be the key in developing sustainable infrastructure in urban areas. This study analyses and discusses an extensive water leak incident taken place throughout the parallel tunnels LUO09 construction in the soft alluvial deposits in Kaohsiung, Taiwan. Dumping sand bags and quick-set cement intervened the incident but in vain. The water leak incident is initiated by the piping. The existing vehicle underpass causes the jet-grout columns installed not exactly in the plumb. Their overlapping is estimated to be less than the design value of 60 cm, and some seepage-prone weak zones are thus developed. The measured hydraulic gradient being equal to 12.1 and existence of seepage-prone weak zones are deemed as the main cause initiating the water leak incident. The pinhole test results highlight not only the nonplastic nature of the Kaohsiung silt but also its vulnerability to piping under large hydraulic gradients. Some bullet points that indicate what engineers should do or avoid are learned and summarised.

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Lubrication performance of pipejacking in soft alluvial deposits

Cited by 70 publications

References 34 publications

Instability Mechanism of Cavity‐Bearing Formation under Tunnel Excavation Disturbance

Instability Mechanism of Cavity‐Bearing Formation under Tunnel Excavation Disturbance

Using Post-Harvest Waste to Improve Shearing Behaviour of Loess and Its Validation by Multiscale Direct Shear Tests

Rethinking the Water Leak Incident of Tunnel LUO09 to Prepare for a Challenging Future

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